It is well known to use apparatus to generate energy from the wind. Typically, high speed propeller-type turbines have been used due to their high efficiency. Such high-speed turbines are generally very large and generally comprise a nacelle mounted for use atop single towers of significant height and diameter. Such turbines may be unidirectional and erected to take advantage of the usual flow of winds through the location in which they are positioned. Alternatively, the nacelle may be capable of turning in a horizontal plane to adjust the direction of the rotor to face into the oncoming wind.
Many different designs of wind turbines are known. Many wind turbines are oriented vertically, having one or more stacked rotors rotatable about a vertical axis such as described in U.S. Pat. No. 4,359,311 to Benesh. Others are mounted on a horizontal axis and have a plurality of blades typically oriented at one end of the horizontal rotor like a traditional windmill. Multi-vaned rotors or windmills are taught in a number of patents including U.S. Pat. No. 6,064,123 to Gislason, U.S. Pat. No. 6,779,966 to Smith II, U.S. Pat. No. 6,069,409 to Fowler et al., and US Patent Application 2005/0015639.
Of particular interest, U.S. Pat. No. 4,838,757 to Benesh teaches a wind turbine having a Savonius-type rotor mounted along a horizontal rotor. The wind turbine is mounted on a frame having wheels which engage a circular track for rotation in yaw. A wind sensor controls the orientation of the wind turbine relative to the direction of the wind and a deflector plate is mounted at an entrance to the blades to augment and smooth the action of the Savonius-type rotor. One or more airfoils assist in ensuring the alternator is not overloaded in high wind conditions.
There is interest in the field of wind power generation for relatively compact wind turbine units which can be readily transported and mounted at remote locations where other sources of power are scarce and which are relatively simple in design, capable of producing sufficient power for the purpose to which they are directed and which are efficient.